never read textbook or memoirs of LKY....

apparently he quit the labour front after coming back from england without achieving independence in talks. he would not accept anything less than that, but the british were only willing to grant self-government status.
he said he would quit the party and resign as chief minister if he failed to secure independence, and had to honour his word. he then verbally challenged lee kuan yew to leave his tg pagar seat (as leader of opposition then and who had openly opposed his rhetoric tactics during the talks and for not being contented with three-quarters independence and coming back with nothing) and he leave his cairnhill seat, and fight it out in a by-election.
lee kuan yew agreed to it, to david's surprise cos he had not thought out his tactics properly then and whether he had the mandate and confidence to win it. david then announced he would quit parliament for good, but actually founded the workers' party before the 1959 elections.
the cairnhill seat he vacated was worn by liberal socialist party, and lee kuan yew won his seat on a stronger margin of 68.13%.
lim yew hock from labour front took over as chief minister, were tough and arrested many communists, and a multi-party went to england and got their approval for self-governance, with joining malaysia as the eventual goal.
david marshall contested and lost in the 1959 elections, but gained his anson by-election seat (vacated cos the MP passed away) on the WP ticket in 1961 apparently with some leftist support. the communists in PAP wanted to show the non-communist in PAP the type of support they could muster, and this prompted lee kuan yew to table the famous motion to seperate the communist from the non-communist in the PAP. they were able to get the half plus one majority in the parliament, and the rest walked over to the other side and banded themselves as the Barisan Sosialis.
* i'm writing from memory, u wan to know the whole thing go read the memoirs of LKY, first book.
quoting from
http://en.wikipedia.org/wiki/David_Saul_Marshall,
"Marshall stayed on the backbench, before quitting the ruling Labour Front party in 1957 and founding the Workers' Party of Singapore. He lost in the 1959 general election, but was able to win a by-election in Anson in 1961. After losing his seat again in 1963, he returned to practise law but remained active in opposition politics until 1972, when J. B. Jeyaretnam became leader of the Workers' Party.
From 1978 to 1993, Marshall served as Singapore's Ambassador to France, Portugal and Switzerland. As Singapore's ambassador, Marshall always defended his country's interests, despite his differences with Lee Kuan Yew's government. He retired from the diplomatic corps in 1993.
He died in 1995 as a result of lung cancer."